1. Field of the Invention
This invention relates to a parking brake device for vehicles and more particularly to improvements in contact structure of a parking brake switch in a manipulating device for the parking brake.
2. Description of the Related Art
Conventionally, a parking brake device of the foot operated pedal type, as shown in Japanese Utility Model Laid Open Application No. 56-21262, has a bracket secured to a vehicle body, a brake pedal rotatably pivoted on the bracket and a switch connected to the bracket by means of a leaf spring. The switch includes a switch actuating means which is actuated by the parking brake pedal when the pedal is returned in its original position.
In the foregoing device, the parking brake pedal is subject to overtravel past its original position, due to inertia, when the pedal is released for its return to its original position. Therefore, due to the inertia arising from the force of the return, a stopper for the pedal may be bent and a leaf spring provided with the switch may be elastically deformed. This prevents the damages of the switch due to the over stroke of the switch actuating means by the parking brake pedal.
The above-discussed switch is of the on-off type which is controlled by the biasing force of a leaf spring and the biasing force of another spring positioned within the switch to urge the switch actuating means against the leaf spring. Difficulty has arisen in setting the spring constants of the two springs and to set the on-off position of the switch. This results in less reliability in the switch operation and in less durability in the switch. In case that the load or biasing force of the leaf spring is substantially less than that of another spring due to differences in manufacturing and assembling of the leaf spring, the switch actuating means moves insufficiently when the parking brake pedal returns and the switch may not be actuated. If the load or biasing force of the leaf spring is excessively larger than that of another switch, the switch actuating means moves a distance greater than the required magnitude and the durability of the switch is less. Furthermore, in the above device, since the amplitude and spring constant of the leaf spring may be the same in both directions when the leaf spring is bent to the bracket, the leaf spring is alternately vibrated in both directions when the parking brake pedal is returned under shock conditions. This results in vibration noises and the durability of the leaf spring per se is decreased. These drawbacks may be overcome by a special arrangement where the switch is directly mounted on the bracket and the magnitude in bending of the stopper is set within the range of the stroke of the switch actuating means. However, this increases noise when the pedal is returned and reduces freedom of the design with a limited mounting of parts.